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Research Papers: Fundamental Issues and Canonical Flows

Flow Similarity in the Rotor–Stator Interaction Affected Region in Prototype and Model Francis Pump-Turbines in Generating Mode

[+] Author and Article Information
Zhongjie Li

Institute of Fluid Machinery and
Fluid Engineering,
Department of Thermal Engineering,
State Key Laboratory of Hydroscience
and Engineering,
Tsinghua University,
Beijing 100084, China
e-mail: lizhongjie1989@163.com

Zhengwei Wang

Professor
Institute of Fluid Machinery and
Fluid Engineering,
Department of Thermal Engineering,
State Key Laboratory of Hydroscience and
Engineering,
Tsinghua University,
Beijing 100084, China
e-mail: wzw@mail.tsinghua.edu.cn

Xianzhu Wei

Harbin Institute of Large Electrical Machinery,
Harbin 150040, China
e-mail: weixianzhu@hit.edu.cn

Daqing Qin

Harbin Institute of Large Electrical Machinery,
Harbin 150040, China
e-mail: qindq@hec-china.com

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received May 31, 2015; final manuscript received November 20, 2015; published online February 17, 2016. Assoc. Editor: Frank C. Visser.

J. Fluids Eng 138(6), 061201 (Feb 17, 2016) (15 pages) Paper No: FE-15-1372; doi: 10.1115/1.4032298 History: Received May 31, 2015; Revised November 20, 2015

Similarities of the flow in the rotor–stator interaction (RSI) affected region (stay vanes, guide vanes, and runner domain) in prototype and model Francis pump-turbines are analyzed using numerical simulations with special attention on the influence of Reynolds number. The ratios of characteristic length and velocity between the prototype and the model are 10.97 and 2.54; thus, the Reynolds numbers differ by about 28 times. Detailed flow analysis argues for higher partial load condition, Q = 0.8Qd, and severe partial load condition, Q = 0.45Qd. The flows in the distributor (spiral casing, stay vanes, and guide vanes domain) are well-behaved for both conditions with no separation, presenting high level of similarity in both space and time domain. The flows in the runners are well-behaved at higher partial load, Q = 0.8Qd, and present good flow similarity and weak Reynolds number effects between the model and the prototype. At severe partial load, Q = 0.45Qd, flow separation develops on the blade pressure sides and partially blocks the runner passages, showing prominent flow discrepancy and stronger Reynolds number effects between the two turbines. For the prototype flow of high Reynolds number, viscous effects have a minor role and less momentum is lost in the boundary layer. Therefore, the flow deceleration is less severe and the emergence of separation is restrained, presenting spatially delayed separation and a less disorganized flow pattern in the prototype. Validated by the model tests and on-site measurements, pressure fluctuations recorded in the vaneless space show that the relative fluctuation amplitudes in the model are slightly higher than those in the prototype. Resorting to dimensionless analytical equations and simulation results, the deviation in pressure fluctuations is found out to be influenced by Reynolds number effects. The research provides an improved understanding of Reynolds number effects on the flow discrepancy and pressure fluctuation difference in the RSI-affected region, which will facilitate better estimations of performance from scale model to prototype.

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Figures

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Fig. 1

Mesh in the prototype runner: (a) overall view of the runner domain and (b) cross-sectional view of the mesh refinement in the boundary layer

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Fig. 2

Grid independence checks

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Fig. 3

Comparisons of efficiencies

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Fig. 4

Time-averaged normalized velocities at the midheight of the distributor with an enlarged view on the right showing contour lines (Q/Qd = 0.8): (a) model and (b) prototype

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Fig. 5

Time-averaged normalized velocities at the midheight of the distributor with an enlarged view on the right showing contour lines (Q/Qd = 0.45): (a) model and (b) prototype

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Fig. 6

Time-averaged normalized velocity |V*| distributions in the distributor

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Fig. 7

Monitoring lines of velocities and measuring point of pressures

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Fig. 8

Time history of normalized velocity |V*| at point P1 in the vaneless space

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Fig. 9

Time-averaged normalized relative velocities W* in the midheight of the model runner (Q/Qd = 0.8): (a) in global coordinate system shown by LIC method and (b) in local coordinate system shown by point-based arrows

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Fig. 10

Time-averaged normalized relative velocity W* in the midheight of the prototype runner (Q/Qd = 0.8): (a) in global coordinate system shown by LIC method and (b) in local coordinate system shown by point-based arrows

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Fig. 11

Time-averaged normalized relative velocity W* in the midheight of the model runner (Q/Qd = 0.45): (a) in global coordinate system and (b) in local coordinate system

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Fig. 12

Time-averaged normalized relative velocity W* in the midheight of the prototype runner (Q/Qd = 0.45): (a) in global coordinate system and (b) in local coordinate system

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Fig. 13

Streamlines grayscaled by the normalized relative velocity |W*| in the runner (Q/Qd = 0.8): (a) model and (b) prototype

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Fig. 14

Time-averaged normalized relative velocity W* in the midheight of the runner, given at radial positions of r/R1 = {0.9, 0.8, 0.7, 0.6, 0.5} (Q/Qd = 0.8): (a) model and (b) prototype

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Fig. 15

Normalized radial (top) and tangential (bottom) velocities in the runner midheight (Q/Qd = 0.8)

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Fig. 16

Streamlines grayscaled by the normalized relative velocity |W*| in the runner (Q/Qd = 0.45): (a) model and (b) prototype

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Fig. 17

Time-averaged normalized relative velocity W* in the midheight of the runner, given at radial positions of r/R1 = {0.9, 0.8, 0.7, 0.6, 0.5} (Q/Qd = 0.45): (a) model and (b) prototype

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Fig. 18

Normalized radial (top) and tangential (bottom) velocities in the runner midheight (Q/Qd = 0.45)

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Fig. 19

The international standard test rig of the HEC

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Fig. 20

Pressure fluctuation spectra at monitoring point P1 (Q/Qd = 0.8)

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Fig. 21

Pressure fluctuation spectra at monitoring point P1 (Q/Qd = 0.45)

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Fig. 22

Comparisons of relative pressure fluctuation amplitudes at point P1

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